Our first NimBUS database was on a dedicated server, but over time we added a couple of very small databases to it to support other applications. This was no problem at all, but any database with a real workload has far more potential to cause problems than ours did. Since then, we have moved NimBUS to a much larger server (64-bit, etc.) but left the other databases on the old server, so now it is on a dedicated host again.
While hardly official or well-informed, I suspect that sharing a database server with other applications should not be a problem for NimBUS by itself. However, database performance is a major consideration, and the more you load a database with busy applications, the more likely they are to interfere with each other. Our NimBUS database is very busy, so we would not dare put anything else on the same server unless it were small and/or not critical. The performance demands of NimBUS will vary significantly based on the size of your environment, so this might still be okay for you.
-Keith